A siRNA mediated hepatic dpp4 knockdown affects lipid, but not glucose metabolism in diabetic mice.

Systemic inhibition of dipeptidyl peptidase 4 (dpp4) represents an effective and established treatment option for type 2 diabetes (T2D). The current study investigated in mice if a liver selective knock-down of dpp4 by therapeutic siRNAs could be a novel, similarly effective treatment option for T2D. Furthermore, the potential effects on hepatic steatosis, inflammation and lipid metabolism were investigated after hepato-selective knock-down of dpp4. The knock-down efficiency and IC50 values of siRNAs targeting dpp4 were analyzed in PC3 cells. In two independent studies, either db/db mice or C57BL/6J mice were injected intravenously with a liposomal formulation of siRNAs targeting either dpp4 or a non-targeting control, followed by metabolically characterization. In comparator groups, additional cohorts of mice were treated with an oral dpp4 inhibitor. In both animal studies, we observed a robust knock-down (~75%) of hepatic dpp4 with a potent siRNA. Hepatic dpp4 knockdown did not significantly affect glucose metabolism or circulating incretin concentrations in both animal studies. However, in obese and diabetic db/db mice hepatic steatosis was reduced and hepatic mRNA expression of acaca, scd1, fasn and pparg was significantly lower after siRNA treatment. Systemic inhibition of the enzymatic dpp4 activity by an oral dpp4 inhibitor significantly improved glucose handling in db/db mice but did not affect hepatic endpoints. These data demonstrate that a targeted reduction of dpp4 expression in the liver may not be sufficient to improve whole-body glucose metabolism in obese and diabetic mice but may improve hepatic lipid metabolism.

LAPS Insulin115: A novel ultra-long-acting basal insulin with a unique action profile.

AIMS: To conduct a comprehensive pre-clinical study of the novel ultra-long acting insulin analogue LAPS Insulin115. METHODS: Pharmacokinetic/pharmacodynamic studies comparing LAPS Insulin115 with other basal insulins were conducted in genetically diabetic (db/db) mice. Insulin signalling in the major target organs was analysed using Western blot after single subcutaneous injection in wild-type male Wistar rats. Using in vitro assays we analysed transendothelial transport, insulin receptor (IR) interaction, and the mitogenic and metabolic properties of LAPS Insulin115. Furthermore, IR downregulation after long-term exposure to high concentrations of LAPS Insulin115 was analysed using an in vitro desensitization/resensitization model. RESULTS: The novel Fc-conjugated insulin derivative LAPS Insulin115 showed an extensively prolonged pharmacokinetic and pharmacodynamic profile in rodents. Despite its size of 59 kDa, LAPS Insulin115 passes the vascular endothelial barrier and induces insulin signalling in all major target tissues in rats. In vitro, LAPS Insulin115 showed a very slow onset of action because of its reduced IR affinity; however, after long-term stimulation it was equipotent in respect to its metabolic potency and showed no increased mitogenic action when compared with regular insulin. Remarkably, under conditions of chronic exposure, LAPS Insulin115 does not induce irreversible desensitization of target cells, which is probably attributable to much less prominent IR downregulation. CONCLUSION: Thus, LAPS Insulin115 exhibits a unique in vivo and in vitro profile and thereby represents an excellent candidate for a once-weekly insulin analogue.